Sheetsxsheet i



Dec. 23, 1952 G. A. TUCK 2,622,589

DRAFT HOOD FOR COMBUSTION APPARATUS Filed Sept. 6, 1949 2 SHEETS-SHEET 1 W K\ B is za I I 7 I 22 V i INVENTOR.

George A. Ti clz 12 TTORNEVS Dec. 23, 1952 a. A. TUCK 2,622,539

DRAFT HOOD FOR COMBUSTION'APPARATUS Filed Se t. 6, 1949 2Sl-IEETS-SHEET 2 INVENTOR. George A Tuck QWUQZMJM flTTORNES S Patented Dec. 23, 1952 DRAFT HOOD FOR COMBUSTION APPARATUS George A. Tuck, San Francisco, Calif., assignor to International Sales Company, San Francisco, Calif., a corporation of California Application September 6, 1949, Serial No. 114,187

7 Claims.

This invention relates generally to so-called draft hoods such as are employed with fuel gas burning appliances.

Heating appliances making use of natural gas or like fuel, and particularly gas fired duct furnaces such as are used for domestic heating systems, commonly employ so-called draft hoods which are connected between the flue of the appliance and the chimney flue or other draft conduit used to carry away the products of combustion.

Gas hoods for use with gas fired duct furnaces for domestic heating systems, must comply with relatively rigid test standards. Thus in a normal installation, blockage of the chimney flue or the outlet from the draft hood must not cause an increase in the concentration of carbon monoxide in the gaseous products of combustion, beyond certain permissible limit-s. When a condition of downdraft occurs from the chimney flue into the draft hood, there must not be any detrimental effect upon the appliance, such as a serious increase in carbon monoxide concentration, or extinguishment of the burner flame. Likewise in the event of a normal updraft applied to the outlet of the draft hood, the appliance should continue to operate without serious disturbance, and the carbon monoxide content of the gases of combustion should not increase beyond permissible limits. just outlined, under normal conditions gaseous products of combustion from the appliance should pass through the draft hood to the chimney flue without escaping into the surrounding atmosphere.

Various types of draft hoods have been constructed in the past to comply with the above requirements. Conventional draft hoods which have been used have been relatively large and bulky, and particularly they have taken too much space for installation where the available space is restricted. When normally installed the draft hood has extended for a considerable distance above the appliance, thus requiring excessive overhead space for a complete appliance installation. A further disadvantage of conventional draft hoods has been that they have not been readily adaptable to different types of appliances, or to different conditions of installation. In addition they have not been adaptable with respect to making connection from the outlet of the hood to the chimney flue. Because of the nature of the baffling employed within the hood, it is necessary to confine the chimney flue connection to one outlet opening in the upper part of the hood,

In addition to the requirements a 2 and thus it is difficult to install the hood in a variety of situations, where, for example, it might be more convenient to change the point of connection between the hood and the chimney flue.

In general it is an object of the present invention to provide a draft hood which will overcome the difficulties of prior conventional constructions of this character.

Another object of the invention is to .provide a draft hood which can be installed with a fuel gas appliance in such a manner as to occupy a minimum amount of space, and which need not extend for any substantial distance above the top of the appliance.

Another object of the invention is to provide a draft hood which can be adjusted to suit different appliances, and appliances of different capacities.

Another object of the invention is to provide a draft hood which is flexible with respect to different installation requirements, and which in particular will enable making outlet connection at a plurality of points on the upper part of the hood, without affecting the ability of the hood to comply with all test requirements.

Further objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a side elevationa1 view illustrating a draft hood incorporating the present invention, and installed in connection with a gas fired duct furnace.

Figure 2 is a cross-sectional view taken along the line 2-2 of Figure 1.

Figure 3 is a cross-sectional view taken along the line 33 of Figure 2.

Figures 4 and 5 are diagrammatic side elevational views, in section, illustrating operation of the hood under normal and abnormal operating conditions.

Figure 6 is a side elevational view in section illustrating another embodiment of the invention.

Figure '7 is a side elevational View of the hood shown in Figure 6, and looking toward the right hand side of the latter.

Figure 8 is a cross-sectional View taken along the line 8-43 of Figure 6.

In Figure 1 of the drawing my draft hood I0 is shown installed in connection with a gas fired duct furnace II. This furnace may for example burn natural fuel gas, and have its hot air ducts connected in a domestic air heating system. The appliance flue l2 communicates with the combustion chamber and carries away the gaseous products of combustion. Pipe I3 is a chimney flue which connects with a chimney or other draft means.

The hood I consists of a housing formed by the sheet metal side walls [6, IT, I8 and I9, together with a top wall 2|. The side walls are connected in the form of a rectangle or square as shown in Figure 2. The lower end of the hood has an unrestricted opening 22 to the surround ing atmosphere.

The one side wall l8, in the lower part of the hood, is provided with an inlet opening 23. A short conduit section may be provided to facilitate connecting the opening 23 with the appliance flue l2. The upper part of the hood has its side walls provided with a plurality of outlet openings 24, 25, 26 and 21, together with short conduit sections 28, 29, 30 and 3|, to facilitate making connection with the chimney flue l3. Normally only one such outlet opening is employed, while the other openings are capped. Thus caps 32, 33 and 34 are shown for the outlet openings 25, 26 and 21, while the opening 24 is shown connnected with the chimney flue I 3. The top wall 2| of the hood is shown provided with a similar outlet opening 36, in conjunction with the conduit section 31, and the closure cap 38.

Intermediate the upper and lower parts of the hood there is a partition wall 39 which is provided with a centrally disposed opening 4| which is illustrated as circular, but which may be otherwise contoured. A collar, or short conduit section 42 is fitted within the opening 4! and is frictionally retained in a desired adjusted position. It is desirable that the passage 43 through the conduit section 42 be about the same diameter as that of the outlet openings 24, 25, 26, 21 and 36.

Assuming that the draft hood is installed substantially as illustrated in Figure 1, the operation can be explained as follows: Normally a continuous draft occurs through the chimney flue l3, to cause a continuous upward flow of air from the surrounding atmosphere through the bottom opening 22, and through the passage 43. Gaseous products of combustion leaving the gas appliance by way of appliance flue l2, commingle with the upward moving current of air flowing through the passage 43, thus delivering the products of combustion into the chimney flue l3. The normal upward flow through the passage 43 is suflicient, under normal chimney draft conditions, to prevent any of the products of combustion from flowing downwardly and out into the atmosphere, through the bottom opening 22. Normal flow through the draft hood as just described is illustrated diagrammatically in Figure 4.

Assuming an abnormal downdraft through the chimney flue l3, this causes a downilow through the passage 43, as illustrated in Figure 5. Flow downwardly from the passage 43 does not create a back pressure upon the appliance flue 12, but on the contrary has an aspirating effect upon the inlet opening 23, whereby products of combustion under such abnormal conditions are delivered into the draft hood, and are discharged through the lower opening 22. Because of the way in which the discharge occurs downwardly from the passage 43, with an aspirating action upon the inlet 23, such abnormal downdraft does not interfere with proper combustion within the gas appliance, and it cannot cause such diificulties as the extinguishment of the gas flame. In the event chimney due [3, or the outlet opening 24, should be blocked, the products of combustion 'ferent operating conditions.

from the appliance find ready egress through the bottom opening 22 into the surrounding atmosphere, and this again occurs without imposing abnormal conditions on the appliance, such as might cause an increase in the carbon monoxide content beyond permissible limits.

A draft hood constructed as described above can be made to comply with all of the test requirements previously described. A particular advantage of the construction is that it can be made in relatively compact form, and it can be installed so that it does not extend to any substantial height beyond the top of the gas appliance. It occupies a relatively small amount of space, in addition to reducing the necessary overhead clearance, and therefore it is well adapted for use with appliances where it is desired to make a highly compact installation. The collar or conduit section 42 can be adjusted vertically within the wall 39, in order to adapt the draft hood to different sized appliances, and dif- Thus when the collar 42 is adjusted to a lower position from that illustrated in the drawing, there is a greater aspirating action upon the inlet opening 23, when a downdraft occurs, to thereby adapt the hood to appliances of a larger size, where a greater quantity of products of combustion must be discharged downwardly through the bottom opening 22, under such abnormal downdraft conditions.

A further advantage of the above construction is that the chimney flue I3 can be connected to any one of the several outlet openings. This greatly facilitates adaptation of the hood to various installation requirements, without resorting to complicated and expensive pipe extensions. Irrespective of the particular outlet opening to which the chimney flue i3 is connected, operation of the draft hood is not affected.

Figures 6 to 8 inclusive illustrate another embodiment of the invention, which makes possible a greater reduction in over-all height. In this instance the hood is formed with the sheet metal sidewalls 4549, together with a top wall 5|. The appliance flue I2 is fitted into an opening 52 formed in the side wall 48. The chimney flue l3 is coupled to the collar 53, and thus connected with the outlet opening 54 in the Wall 46. It will be noted that the axes of openings 52 and 54 are ofiset vertically, but not to the same extent as in the previous embodiment described (see Figure 1). The lower end of the hood is formed to provide the opening 55 to the atmosphere.

Within the hood there is a partition wall 56 which corresponds generally to the partition wall 39 of Figures 1 to 5. However wall 56 is inclined with respect to the horizontal as illustrated particularly in Figure 6, whereby its upper edge portion extends from a position above the opening 52, and its lower edge portion extends below the outlet opening 54. Mounted upon the partition 53 there is a collar or short conduit section 5! which serves to form a connecting passage 58 between the upper and lower portions of the hood. Note that the collar 51 in this instance is contoured to be oval as shown in Figure 8, and the proportions employed are such that the passage 58 is ample for the appliances and draft conditions for which the hood is to be used. The upper end of the collar 51 terminates in a substantially horizontal plane as shown in Figure 6.

Operation of the embodiment illustrated in Figures 6 to 8 is similar to that previously described with reference to Figures 1 to 5. Normally the upward draft through the chimney flue I3 causes a continuous upward flow of air from the surrounding atmosphere through the bottom opening 55. Gaseous products of combustion leaving the gas appliance by way of appliance flue I2, commingle with the upward moving current of air flowing through passage 58, thus delivering the products of combustion, diluted by mixture with atmospheric air, into the chimney flue l3. The normal upward flow through the passage 58 is suficient under normal chimney draft conditions to prevent any of the products of combustion from flowing downwardly and out into the atmosphere, through the bottom opening 55.

Assuming an abnormal downdraft through the chimney flue l3, the resulting downward flow through the passage 58 does not create a back pressure upon the appliance flue I2, but

likewise has an aspirating action upon the inlet opening 52, whereby products of combustion under such abnormal conditions are delivered into the draft hood and thence discharged through the lower opening 55. Likewise downward dis charge from passage 58 has an aspirating action upon the inlet opening 52 whereby such abnormal downdraft does not interfere with proper combustion within the gas appliance, and cannot cause such difficulties as extinguishment of the gas flame. In the event the chimney flue l3 or the outlet opening 54 should be blocked, the products of combustion from the appliance find ready egress through the bottom opening 55 to the surrounding atmosphere without imposing abnormal conditions on the appliance.

I claim:

1. A draft hood for heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, a housing having a downwardly faced lower open end, an inlet opening communicating through one side of the lower portion of the housing and adapted to make connection to the appliance flue, an outlet opening communicating through one wall of the upper portion of the housing for making connection with a chimney flue, a partition wall within the housing and disposed intermediate the upper and lower portions of the same, said wall having an opening through the same forming a passageway which is located intermediate spaced vertical planes coincident with the side margins of the inlet opening for communication between the upper and lower portions of the housing, said opening also being located in close- 1y adjacent but spaced proximity with said inlet opening whereby downdraft through the same aspirates gaseous products of combustion from the appliance flue and discharges the same through the lower opening of the hood.

2. A draft hood for fuel gas heating appliances of the type having an appliance flue for dis charge of gaseous products of combustion, a housing having a lower open end, an inlet opening communicating through one side wall of the lower portion of said housing and adapted to make connection to the appliance flue, an outlet opening communicating through one wall of the upper portion of the housing for making connection with a chimney flue, and a partition wall within the housing and disposed intermediate the upper and lower portions of the same, said wall having a centrally located opening therethrough to form a passageway intercommunicating between the upper and lower portions of the housing, said passageway being disposed in closely adjacent but spaced proximity with said inlet opening to direct abnormal downdraft downwardly across said inlet opening and through the lower open end of the hood.

3. A draft hood for fuel gas heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, said hood comprising a housing having a lower open end, an inlet opening communicating through one side wall of the lower portion of the housing and adapted to make connection to the appliance flue, an outlet opening communicating through one wall of the upper portion of the housing for making connection with a chimney flue, a partition wall positioned within the housing and disposed intermediate the upper and lower portions of the same, said wall having a centrally located opening therethrough, and a collar-like conduit section communicating with said opening, and carried by said partition wall, said conduit section forming a passageway establishing communication between the upper and lower portions of the housing, said passageway being disposed in closely adjacent but spaced proximity with the inlet opening to direct abnormal downdraft downwardly across said inlet opening and through the lower open end of the hood.

4. A draft hood for fuel gas heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, a housing having a lower open end, an opening communicating through one side wall of the lower portion of the housing for making connection to the appliance flue, an outlet opening communicating through one Wall of the upper portion of the housing for making connection with a chimney flue, a partition wall positioned within the housing and disposed intermediate the upper and lower portions of the same, said wall having a centrally located opening in the same, and a collar-like conduit section fitted within said opening and adjustable in a vertical direction relative to the side walls of the housing, said conduit section forming a passageway which establishes communication between the upper and lower portions of the housing, said passageway being disposed in closely adjacent but spaced proximity with the inlet opening to direct abnormal downdraft downwardly across said inlet opening and through the lower open end of the hood.

5. A draft hood for fuel gas heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, a housing having a lower open end, an inlet opening communicating through one side wall of the lower portion of the housing for making connection to the appliance flue, a plurality of outlet openings communicating through the side walls of the upper portion of the housing, any one of said outlet openings being adapted for connection with a chimney flue, a partition wall positioned within the housing and disposed intermediate the upper and lower portions of the same, wall having a centrally disposed opening therethrough, and a collar-like conduit section fitted within said opening and carried by the partition wall, said conduit section forming a passageway which establishes communication. between the upper and lower portions of the housing, the axis of the conduit section being generally at right angles to and coincident with the axis of the inlet opening.

6. A draft hood for fuel gas heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, a housing having a lower open end, a horizontally extending inlet opening communicating through one side wall of the housing and adapted to make connection to the appliance flue, an outlet opening communicating through another wall'of the upper portion of the housing for making connection with a chimney flue, a partition Wall within the housing and disposed intermediate the upper and lower portions of the same, said wall being inclined with respect to the horizontal and having an upper edge portion terminating adjacent the upper portion of the inlet opening and a lower edge portion terminating adjacent the lower portion of the outlet opening, said wall having a vertically extending opening therethrough which is located between vertical parallel planes coincident with the side margins of the inlet opening for establishing communication between the upper and lower housing portions, said opening also being located in closely adjacent but spaced proximity with the inlet opening whereby downdraft through the same aspirates gaseous products of combustion from the appliance flue and discharges the same through the lower opening of the hood.

7. A draft hood for fuel gas heating appliances of the type having an appliance flue for discharge of gaseous products of combustion, a housing having a lower open end, an opening communicating through one side wall of the lower portion of said housing and adapted to make connection to the appliance flue, an outlet opening communicating through the opposite side wall of the housing and at a higher elevation than said first named opening, said outlet opening being adapted for making connection with a chimney flue, a partition wall disposed within the housing and disposed intermediate the upper and lower portions of the same, said partition wall being inclined with respect to the horizontal and having its upper edge portion terminating adjacent the upper portion of the inlet opening and a lower edge portion terminating adjacent the lower portion of the outlet opening, said wall having an opening therethrough for establishing communication between the upper and the lower housing portions, and a collar mounted on said partition wall and serving with said opening to form a substantially vertically extending passage communicating between said housing portions and disposed in closely adjacent but spaced proximity with the inlet opening, the central axis of said collar being generally disposed at right angles to the axis of the inlet opening and generally coincident with the same whereby downdraft through said collar causes gaseous products of combustion to be aspirated from the inlet openmg.

GEORGE A. TUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,751,798 Dibble Mar. 25, 1930 2,257,240 Livar Sept. 30, 1941 FOREIGN PATENTS Number Country Date 37,270 Netherlands Jan. 15, 1936 

